This invention relates to the valve art, and, more particularly, to butterfly, ball and plug valves.
The invention is particularly applicable to a new and improved stop cam arrangement for limiting handle rotation to a pre-selected angular degree and for selective adjustment of stop limit locations to position a valve sealing member at optimum efficiency open and closed positions. However, it will become readily apparent to those skilled in the art that the invention is capable of broader applications and could be adapted for use in other types and styles of cam stop arrangements.
Ball valve constructions in commercial use typically employ many different types of stop arrangements useful for ball, butterfly or plug-type valves. Standard butterfly and ball valves usually require a ninety degree movement to take the valve element between a full open and a full closed position. Since an operator typically has no way of knowing the orientation of a valve element mounted in a valve body, handle stop and direction indicators located on the valve allow an operator to generally determine the valve element orientation and to thereby open or close the valve to a full open or full flow position, a fully closed position, or an intermediate limited flow position.
The various forms and types of stop cam arrangements which have heretofore been employed in the valve industry have met with varying degrees of success in that some of the devices have suffered from limited practical value.
Typically, a stop cam arrangement will comprise a flange or extending element depending from the valve handle and disposed for engagement with a portion of the valve body or a protrusion thereon. Although such prior known arrangements have been successful in limiting handle rotation to a particular degree, they have all suffered from one substantial problem. Often, tolerance stacking during the manufacturing process results in the valve element being slightly out of line or cocked with the valve inlet and outlet ports. Such a misalignment has caused less than optimum flow through the valve when open, due to the obstruction of a cocked valve element, and may even cause valve leaking when a stop position is so misaligned as to fail to orient the valve element in a sealing position. Consequently, it is desirable and, often times necessary, to adjust the handle limit stops to achieve the desired and optimum valve element alignments at the open and closed positions.
Although adjustable stop cam arrangements are known for adjusting the limits of movement of a valve sealing member, such adjustable stop elements have comprised clamped or threaded members which are necessarily independently adjustable to define the stop points. Such independent adjustment of stop limits too often allows a variance in the range of movement in the valve element and in the position of the stops for a valve handle. In other words, since one end of the valve movement is always adjustable by one element and the other end of the valve movement is adjustable by another element, there can be no corresponding adjustment of the opposite end of valve path movement upon adjustment of a first end. Such non-corresponding adjustment has resulted in problems and difficulty in setting the handle stop limits and in complicating the manufacturing process.
More specifically, although alignment of a valve element such as ball member having a fluid flow opening may be easily visibly detectible in the fully open position, the fully closed position may not be so easily determined. Accordingly, some conjecture is involved in setting an independently setable closed stop limit after having first independently set an open stop limit.
It has, therefore, been desired to develop a constant displacement dual position cam stop assembly for a valve which could be employed to selectively set the valve element stop limits to align the valve element in an optimum full flow open position and correspondingly a fully closed position. Preferably, such a design would eliminate the problems of non-alignment caused by tolerance stacking during manufacture of the valve.
The present invention contemplates a new and improved dual position cam stop assembly which overcomes all of the above referred to problems and others to provide a new and improved cam stop arrangement which facilitates increased manufacturing efficiency in construction and setting of valve element stop limits, is simple in design, economical to manufacture and readily adaptable to a plurality of type of valves having a variety of dimensional characteristics.